Image acquisition devices such as cameras typically use optical zoom techniques, digital zoom techniques, or a combination of both to allow a user to narrow the viewing angle of an image and to enlarge an object within the image. While optical zoom techniques typically involve adjusting the optical properties of lenses in the camera, digital zoom techniques involve manipulating image data by cropping a region within a full color image and resizing the cropped region back to the full size of the original image.
For example, in a full image with a resolution of 1920×1080, a zoom factor of two can be achieved by identifying a 960×540 region in the image and resizing the region back to 1920×1080. The process of resizing the cropped region involves pixel interpolation because the zoomed image has twice as many pixels as the cropped region, and thus in order to determine values for all the pixels in the zoomed image, a pixel interpolation algorithm must be used. Pixel interpolation algorithms typically involve degradation of image quality.
In spite of this image degradation, digital zoom is still a highly desired feature on digital image acquisition devices because it can be used to increase the zoom achieved by optical zoom techniques, and some devices, such as smartphones, are incompatible with optical zoom because optical zoom requires moving parts. Accordingly, there exists in the art a need for a digital zoom technique that minimizes image degradation but also can be implemented using limited hardware resources like those found in smartphones.
The approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, it should not be assumed that any of the approaches described in this section qualify as prior art merely by virtue of their inclusion in this section.